It is particularly preferred to employ Staphylococcal genes and gene products as targets for the development of antibiotics. The Staphylococci make up a medically important genera of microbes. They are known to produce two types of disease, invasive and toxigenic. Invasive infections arc characterized generally by abscess formation effecting both skin surfaces and deep tissues. S. aureus is the second leading cause of bacteremia in cancer patients. Osteomyelitis, septic arthritis, septic thrombophlebitis and acute bacterial endocarditis are also relatively common. There are at least three clinical conditions resulting from the toxigenic properties of Staphylococci. The manifestation of these diseases result from the actions of exotoxins as opposed to tissue invasion and bacteremia. These conditions include: Staphylococcal food poisoning, scalded skin syndrome and toxic shock syndrome.
The frequency of Staphylococcus aureus infections has risen dramatically in the past 20 years. This has been attributed to the emergence of multiply antibiotic resistant strains and an increasing population of people with weakened immune systems. It is no longer uncommon to isolate Staphylococcus aureus strains which are resistant to some or all of the standard antibiotics. This has created a demand for both new anti-microbial agents and diagnostic tests for this organism.
DbpA of E. coli is a member of the DEAD-type ATP-dependent RNA helicases. Both ATPase and RNA helicase activities of DbpA have been demonstrated in E. coli. Since DbpA hydrolyzes ATP only in the presence of bacterial 23S rRNA and it is able to unwind 16S and 23S rRNA hybrids, it has been strongly implicated in the important biological process of ribosomal assembly. Two other E. coli DbpA hoinologues, SrmB and DeaD (CsdA), are also implicated in ribosomal biogenesis since overexpression of deaD and srmB can suppress the effect of a temperature-sensitive mutation in L24, a protein that is necessary for the assembly of the large ribosomal subunit, and in the rpsB gene encoding the ribosomal protein S2, respectively. RhlB of E. coli, another DbpA homologue, is a major component of RNA degradosome which is important in RNA processing and messenger RNA degradation. The eIF4A, the eukaryotic homologue of DbpA, is involved in initiation of translation. There are eight conserved domains in the DEAD box proteins and all these are also found in the DbpB of S. aureus. Therefore, it is very likely that the DbpB of S. aureus could play an important role in the ribosomal assembly, translation, or RNA processing and mRNA turnover.
Clearly, there is a need for factors, such as the novel compounds of the invention, that have a present benefit of being useful to screen compounds for antibiotic activity. Such factors are also useful to determine their role in pathogenesis of infection, dysfunction and disease. There is also a need for identification and characterization of such factors and their antagonists and agonists which can play a role in preventing, ameliorating or correcting infections, dysfunctions or diseases.
The polypeptides of the invention have amino acid sequence homology to a known E. coli dbpA protein. See Iggo, R., Picksley, S., Southgate, J., McPheat, J., Lane, D. P. 1990, Nucleic Acids Res., 18:5413-5417; EMBL Accession Number: X52647. Also see Fuller-Pace, F. V., et al 1993, EMBO J. 12, 3619-3626.; Nicol, S. M., and Fuller-Pace, F. V. 1995. Proc. Natl. Acad. Sci. USA. 92, 11681-11685; and Boddeker N., et al. 1997. Nucleic Acids Res. 25, 537-545.